Different roles of cerium substitution and oxygen reduction in transport inPr2−xCexCuO4thin films

Abstract

Using pulsed-laser ablation with an improved oxygen annealing process and Hall effect measurements, we show that the reduction process needed to induce superconductivity in electron-doped cuprates thin films does not trigger a significant change in carrier concentration (or band filling) contrary to cerium substitution. We show that it has, however, a severe impact on hole-type carrier mobility. This feature is evidenced by focusing on the overdoped regime $(x\ensuremath{\ge}0.16)$ for which reduction increases the contributions of hole-type quasiparticle excitations to the Hall coefficient without affecting much the contribution from electrons. Since reduction has been also shown recently to provoke a strong suppression of antiferromagnetic order for doping close to optimal, we interpret the strong increase in mobility to result from a decreasing scattering rate related to a decreasing strength of antiferromagnetic correlations. We suggest that delocalization of hole-type carriers with reduction is achieved through the frustration of the antiferromagnetic order of as-grown nonsuperconducting composition by in-plane oxygen vacancies. We propose a comparison of ARPES data for as-grown and reduced ${\mathrm{Pr}}_{2\ensuremath{-}x}{\mathrm{Ce}}_{x}{\mathrm{CuO}}_{4}$ on the overdoped side as a possible experiment to clarify the origin of the hole-type quasiparticles with reduction.